Aircraft brakes, which are often made of carbon-carbon composite materials, are subjected to high temperatures, which may change the properties of the carbon and the friction surface and lead to variation in the friction performance of the brake. Other factors that may increase variation in friction performance of carbon-carbon composite materials are variation in the carbon microstructure, variation in the fiber/matrix ratio, and differences in the energy levels of the previous stop or stops performed by the brake. In addition to consistent friction performance, another desirable property of a carbon-carbon friction material is a low wear rate.
It had previously been discovered that titanium carbide, when uniformly distributed into carbon-carbon composite preforms in the form of particles of particular particle size, provides the preforms with beneficially modified friction and wear properties. See U.S. patent application Ser. No. 10/980,033, filed Nov. 3, 2004. The entire disclosure of Ser. No. 10/980,033 is expressly incorporated by reference herein.
The uniform distribution of titanium carbide particles in Ser. No. 10/980,033 contemplates the formation of a fibrous matrix and incorporating titanium carbide powder into the fibrous matrix. However, for example, when manufacturing carbon fiber preforms having needled nonwoven carbon fiber matrices, the preforms are typically carbonized prior to densification. At this point, it is not possible to evenly distribute fine particles of titanium carbide throughout the preform.